View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Wits Institutional Repository on DSPACE C O N T R A S T I N G G R O W T H T R A I T S A N D I N S E C T I N T E R A C T I O N S O F T W O T A M A R I X S P E C I E S A N D A H Y B R I D ( T A M A R I C A C E A E ) U S E D F O R M I N E R E H A B I L I T A T I O N I N S O U T H A F R I C A Lael Edith Buckham A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science. School of Animal, Plant and Environmental Sciences, Johannesburg, October 2011 DECLARATION I declare that this research report is my own, unaided work. It is being submitted for the Degree of Master of Science in the University of the Witwatersrand, Johannesburg. It has not been submitted before for any degree or examination in any other University. ____________________ Lael Edith Buckham 10th day of October 2011. i ABSTRACT Both indigenous “Tamarix usneoides” and alien T. ramosissima co-occur in South Africa. Tamarix usneoides is potentially a metal and salt phytoremediation species. However, hybridisation is occurring between the two species and hybrids growth characteristics are deemed to be invasive. This study was undertaken at two sites on one Highveld gold mine, characterised by different soil types, where plant growth, reproductive potential and insect abundance and diversity were measured. This aims to establish the growth of T. usneoides in two site-species trials, and to identify differences between Tamarix taxa that are consistent across different environmental conditions and can be used for identification. This study also set out to establish if higher reproductive effort and enemy release are promoting the invasiveness of T. ramosissima. Trees in one site (a water logged, clayey “Glenrosa” soil) displayed significantly greater percentage survival, growth and reproductive effort than trees in the other site (a well drained, sandy “Hutton” soil). Extensive hybridisation between T. usneoides and T. ramosissima was observed with two hybrid states, morphologically similar to each parent species. The reproductive effort is consistently greater in T. ramosissima and T. ramosissima hybrid than T. usneoides and T. usneoides hybrid. After sampling 217 trees in this study, the three characteristics of (1) insertion of filaments into the nectar disc, (2) petal shape and (3) presence of salt glands on leaves most accurately distinguished between T. usneoides and T. ramosissima taxa. Three insect species have been identified from this study as potentially damaging agents on Tamarix spp. Insects can discern between the Tamarix tree taxa and T. ramosissima is being released from insect herbivore pressure, as very few insects and a lower diversity were recorded on T. ramosissima and its hybrids (T. ramosissima hybrids > T. ramosissima). To achieve phytoremediation objectives, careful tree identification and selection of genetically pure individuals for cloning is recommended. Additionally the removal of existing alien and hybrid plants, and further research to find a suitable host specific insect biological agent to control alien Tamarix is necessary. ii DEDICATION I dedicate this work to my family, particularly my father Norman Buckham who has always inspired and encouraged me, my mother Faith Buckham who has taught me to persevere and never give up, and my husband for being my source of fun and joy. I am very grateful for their support and financial assistance during this research. The patience and kindness of my supervisor is also greatly appreciated. I would also like to thank all the special people in my life that have encouraged me and made me believe I could finish this. iii ACKNOWLEDGEMENTS This study was conducted under the Mine Woodlands Project at the University of Witwatersrand and AngloGold Ashanti Ltd (AGA). I am very grateful to my supervisors particularly Prof Marcus Byrne for his valuable time and assistance throughout this tough project, and Isabel Weiersbye for financial assistance and guidance. I thank AGA S.A. Region for enabling me to carry out my research and for financial support (NRF and DTI THRIP grant no. TP2009072900036 to Isabel Weiersbye and Ed Witkowski). I thank all my fieldwork assistants and individuals involved in this project, particularly Benjamin Oageng, Mark Cooper, Lorato Letsholo, Jenny Botha and David Furniss. I also thank Christien Bredenkamp for her valuable time and guidance throughout this project and for helping me unravel the mystery of plant hybridisation. I appreciate the involvement of Glynis Goodman-Cron and thank her for assistance with the morphological identification of plant specimens. I thank the specialists and Vivienne Uys at the Agricultural Research Council (ARC) for insect identification. I appreciate the assistance given by Vivienne Williams with the diversity statistics. iv TABLE OF CONTENTS DECLARATION ..................................................................................................... i ABSTRACT ............................................................................................................ ii DEDICATION ....................................................................................................... iii ACKNOWLEDGEMENTS ................................................................................... iv CHAPTER 1: .......................................................................................................... 1 INTRODUCTION .................................................................................................. 1 1.1 Project Overview ...................................................................................... 1 1.2 Project Aims, Objectives and Limitations ................................................ 3 CHAPTER 2: .......................................................................................................... 5 LITERATURE REVIEW........................................................................................ 5 2.1 Invasive Alien Plants ................................................................................ 5 2.1.1 Enemy Release Hypothesis and IAPs .............................................. 6 2.1.2 Species Relatedness Hypothesis ...................................................... 7 2.2 Genus Tamarix ......................................................................................... 8 2.2.1 Tamarix usneoides (E. Mey ex. Bunge) ........................................... 9 2.2.2 Tamarix ramosissima (Ledeb.) ...................................................... 10 2.2.3 Hybridisation between Tamarix usneoides and Tamarix ramosissima .................................................................................................. 11 2.3 Control of woody Invasive Alien Plants (IAPs) like Tamarix ............... 12 2.4 Phytoremediation .................................................................................... 15 2.4.1 The Mine Woodlands Research Project ......................................... 16 2.4.2 Origin of T. usneoides and putative hybrids in the Mine Woodlands Project (MWP) site species trials .................................................................. 18 2.5 Waste Production from Gold Mining ..................................................... 19 2.6 Legislation pertaining to Gold Mining ................................................... 21 CHAPTER 3: ........................................................................................................ 23 MATERIALS AND METHODS USED TO STUDY TREE GROWTH, REPRODUCTIVE POTENTIAL AND INSECT OCCURENCE ON TAMARIX SPECIES ............................................................................................................... 23 3.1 Introduction to Experimental Techniques .............................................. 23 3.1.1 Mispah (M) Good Soil Site ............................................................ 23 3.1.2 West Complex (WC) Poor Soil Site............................................... 24 3.2 Physical Description of Study Area ...................................................... 25 3.3 Site Layout ............................................................................................. 26 v 3.4 Experimental Procedures ........................................................................ 27 3.4.1 Tamarix Identification ..................................................................... 27 3.4.2 Tree Growth .................................................................................... 30 3.4.3 Flowering Frequency ...................................................................... 32 3.4.4 Insect Identification ......................................................................... 32 3.4.5 Insect Sampling and Data Analysis................................................. 33 3.4.5.1 Tree sweeping (TSW) method ................................................. 34 3.4.5.2 Emergence box method (EMB) ............................................... 36 3.4.5.3 Species accumulation curves ................................................... 36 3.4.5.4 Insect identification.................................................................. 36 3.4.6 Statistical Analysis ......................................................................... 37 CHAPTER 4: ........................................................................................................ 38 RESULTS OF TREE IDENTITY,